Signaling by ultra-audible sound waves



Nov. 24, 9 V 1,562,950

R. A. FESSENDEN SIGNALING BY ULTRA AUDIBLE SOUND WAVES Filed Dec. 14, 1918 2 eetSSheet 1 WITNESS:

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To all whom concern: Y

Be it'known that I, Rnomem A. FEW-- mm, of Brookline, in the county of Norfolk and State of Massachusetts, a citizen of the United States, have invented new and useful Improvements in signahng by Ultra-Audible Sound Waves, of which the said anacysms in the form of a beam.

The accompanyindg} drawings, Figures 1 and 2, show partly. agrammatlcally, means adapted for carrying out my invention.

The present ap hcation is in part a continuation of U. application Serial No. 35,957 filed June 23, 1915, so far as it relates to those parts which are common to the. two specifications more particularly the description on pa e 31 of said application 35,957. Thisapplication, Serial No. 35,957, contained a number of inventions a-patent on one of which was issued'No. 1,265,776, May 14., 1918.

Applicant in 1912 designed and built the type of apparatus called an oscillator, and described in U. S. Patent No. 1167366 (issued J an. 4, 1916) for submarine telegrap'hy and telephony over long distances.

In the course of thee erimental work, applicant applied one of his 500 cycle wireless U. S. Patent No. 918,306 (issued April 13, 1909), and giving a frequency of approximately 50,000- cycles per second, to one of these oscillators, and discovered that when so connected the oscillator radiated an intense stream of' ultra-audible sound waves, and that the radiation tookthe form of a beam like that of a search light.

As no scientific name has as yet been given to such ultra-audible sounda,- appIlt o.

cant in his Report, Navy Department,

22, December 11,1912, has termed these anacysms, and the term is used with this meaningin the present application.

Figure 1 is 'a diagrammatic view illustrating means for generating anacysms.

generating sets, of the type shown in- Figure 2 is a similar view illustratin "one of the methods.

Figure 3 is a dia trating the theory 0 in lpart of this invention. I o igure 4 .is a modification of part of Figure 2.

aromatic .-view* illus- 11 is an oscillator, 13 is one of applicants high frequency alternators, for example, of the 'type described in' U. S. Patent No. 706,737, (issued August 12,

June 21, 1910), having a frequency of the cies of 200,000 or higher may .be used.

-When the key, 12, is pressed down, the

high frequency current flowing through the oscillator causes anacysms of a the subject involved, H

1902), and U. S. Patent/No. 962,018 (issued .order of 50;)00 per second, though frequ'enj frequency of 50,000 per-second to be emitted in the form of a beam, as shown at 14.

The reason that the anacysms are emitted in the form of a beam applicant has-found to. be due to the fact that the uarter wave length of the anacysms is of a 'fl'erent and lower order of ma itude than that of the diameter of the oscillator. For example, the oscillator diaphragm may have a diameter of twenty inches, while the quarter wave length of compressional waves of a fre- Applicant has found at the larger at quency of 50,000 er second will be, in water, only about oneourth of an inch, i. e.', the

ratio of the diameter of .the oscillator to the quarter wave length of the anacysms, the "more definite will be the beam, and the spread of the beam may be varied by vary-' ing the frequency.

Referring to Figure 3, if a line be laid off representing the diaphragm of an oscillator 11, and say forty points at equal distances from each other a complete interference with the exception of a few narrow zones ofinterference fringes exce t in that portion directly in front of the me indicating the oscillator diaphragm.

e laid off on that line and from each point a circle be struck 'sa ten In other words, sound waves emtted from a source, large compared with a. quarter of a wave length of the sound waves, annul each other except directly in front of the source and so produce theie ffect of a beam. For obvious reasons this cannot be fully illustrated in a drawing of the size required by the rules, but it is approximately indicated in Figure 3 where it will be noted that at the point A directly in front of the diaphragm of the oscillator 11 the circles B all cross showing a path of slight interference.

A convenient method of receiving the anacysms is shown on the left hand of Figure 1, where 16 is an oscillator, 17 a rectifier of any suitable type, for example, a crystal rectifier, and 18 is a telephone receiver.

011 the beam ofanacysms falling on the diaphragm of 16, high frequenc oscilla tions of a periodicity of 50,000 wi l he generated by the oscillator, and these being rectified by the rectifier 17, will produce a current in the receiver 18, and if the beam of anacysms is rendered discontinuous by means of the key, 12, a sound will be heard in the receiver, 18.

Such a beam of anacysms may be used to detect the passage of a submarine, 15, between the oscillator, 11, and the oscillator, 16, as so lon as the beam 14: reaches 16, signals made y the key 12, or any suitable conducting device will be heard on the receiver 18, but if the submarine 15, passing down a channel, comes between the oscillators 11 and 16, the beam will be interrupted and no sound will be heard on the receiver 18, thereby indicating the presence of the submarine, -15.

In Figure 2 is shown the application of a beam ofanacysms to the detection of a submarine, 32, by means of reflection, as described in Report to U. S. Navy Department N0. 83, Feb. 19 1917.

As therein described, on throwing the switch 28 upwards so as to connect the 0scillator 27 with the high frequency generator, 30, and depressing the key 29, for a short time, for example, one second, a beam of anacysms will be thrown out as shown. On this beam striking the submarine 32, which may be a mile away, it will be reflected back, if the surface is smooth, as a continuous reflected beam, or if the surface is rough, or the medium turbid as interference fringes of sound i. e., discontinuous trains of sound waves, as described in applicants U. S. Patent No. 1,217,585 (filed April 2, 1914, and issued Feb. 27 1917).

' If the submarine 32 is a mile away from the oscillator 27, the emission from the oscillator 27 will have ceased beforethe beam strikes the submarine 32, and if immediately after opening the key 29, the switch 28 is thrown down into the position shown, the beam or sound diffraction fringes reflected phone terminals to another high frequency generator, 31, giving a frequency of, for example, 51,000 per second. 7

If this is done, then beats will be produced between the two sets of oscillations, and an audible sound will be emitted, this method of receiving being known as applicants heterodyne method.

If desired, the second high frequency generator 31, and the switch 28 may be omitted, and the terminals of the dynamo, 30, permanently connected to the terminals of the oscillator 27, and the motor 301 driving the dynamo 30 disconnected as at 291 from the source of power E at the instant of depressing the key 29, so that the speed of the dynamo 30 gradually falls, while thekey 29 is being held down. This construction is shown' in Figure 4.

Applicant has discovered that when this IS the case, the frequency of the anacysms reflected from 32 will be higher than the frequency of the oscillations which arebeing generated by the dynamo 30 at the instant when the reflected anacysms come back again" and strike the diaphragm of the oscillator 27, and generate oscillations in the oscillator windings, and therefore on the terminals of the-electrostatic telephone receiver 24,,and hiesnce beats will be produced in this case a o.

Applicant has also discovered that the greater the distance the submarine 32 is away from the oscillator 27, the higher will be the pitch of the beats produced by the reflected anacysms, and that in this way the distance of the submarine from the osciI lator 27 can be determined by noting the rate at which the high frequency dynamo 30 is' slowing down, and the frequency of the beats in the electrostatic telephonercceiver 24.

Still another method of sending and receiving these anacysms is shown in the left hand of Figure 2, where 19 and 20 are the terminals, and 21 the dielectric of a condenser receiver of the type shown in applicants U, S. Patent No. 1,182,843 (issued May 9, 1916), 22 is a key, and 25, 26, the fixed and movable plates of aflcondenser receiver 2 1, of the type shown in applicants U. S. Patent No. 7 93,649, (issued July 4, 1905). :1

Ondepessing the key22, anacysms will be sent-out from the condenser 19, 20, 21,- or

if the key 22 is held down and anacysms of a different frequency from that generated by the high frequency dynamo 23 migmgeupon the condenser 19, 20, 21, heter'o yne' beats will be created, and a musical'not'e will be produced in the condenser rece1ver 24.'

The methods and apparatus described in the resent application were disclosed to the U. Na

vy. in 1914, -e' ially their use 1n connection with detectmg submarines (see Report, U.-S. 'Navy Department No. 22,

December 11, 1912, also short duration, such as a short impulse or waves. See Ra and Rayleighs collected papers, article an irre a group consisting of a few waves, strikes ar object whose dimensions are n the tiuarter'. wave length of the larger t eighs Theory of Sound Polish;

Detection by scattering has been described by other inventors; for example, Richardnon-existent.

son British Patent 9423/1912, page 3, lines 17-33; also' Richardsons British Patent 11,125/1912,\page 4, line '55 and page 5, lines 17and18. a

Applicant, however, does not use scattering, but prefers to use interference. Interference does not-occur with short lmpulses,

' but long trains of waves are required. For

example, in the method described in this ap' plication the trains preferably consist of thousands of waves and'a train of 100 waves is necessary in order to produce a single beat or interference fringe.

On actual tests applicant has found a great difference between the results obtained from scattering and from interference. For example, when a sound of short duration (as for. example Richardsons British .Patent 11,125/1912) was sent out against an iceberg or ship in very few cases was any echo observed, in fact an echo was substantially On the other hand when a prolonged train of waves was sent out the waves reflected from the body of the iceberg.

and probably reflected again from thesurface of the water formed interference fringes and in every single case-i. e. 100%. of the singnals senta series of short sounds were received back, due to interference fringes. This also held without exception even when the reflecting object was-the smooth side of a ship. As Richardson points out (British Patent 11,125/1912, page 5, lines 17 and 18) an echo cannot be expected from a smooth ts have been obtained by the.

body like the side of a ship whenscatteringmethods are used, but with applicants inter-- ference method echoes were received on every occasion because the ener where and with the pro onged trams Jof waves sooner or later interference fringes are formed which affect the receiver.

It is alsoto be noted that theheterodyne method of reception-performs anew and useful function in connection with. anacysms from what it does in the m'ethodsdisclosed m appllcants original heterodyne patents.

must go 1 some-f This if for the reason that in wireless teleg-- V raphy the motion of the stations is negligi ble in comparison with the velocity of trans mission and consequently there is no Doeppler effect. and the received frequency remains constant. On the other hand with anacysms the sources are generally in motion and there" is a very pronounced Deeppler efiect andit would beimpossible to tell what frequency to listen in on unless the direction and velocity of the object were known, but with .the heterodyne method used in connection with anacysms, as described in' the specification, it does not matter what the received frequency may be as this will merely vary the number of beats per second, which is a second new and useful function. The invention herein described my be applied to signalin in air aswell as through water, for examp e,-from or to aeroplanes.

What I claim i's 1. In a system :of signaling by high freau'dib e sound vibrations by the motion of a 7 surface having a large ratio of the diameter of the surface to the wave length ofsaid sound vibrations at an ultra-audible 'frequency and having all-of said surface vibrat ing in substantially the same phase.

2. In a system of signaling by high frequency sound vibrations, the-method of producing a beam of sound by generating ultraaudible sound vibrations by the motion of a surface having its diameter of a larger and different order ofma nitude than the quarter wave length of said sound vibrations at an ultra-audible frequency, and having all of said surface vibrating in substantially the same phase. i

3. In a system of signaling by high frequency sound vibrations, the method of producing a beam of sound by generating ultraaudible sound vibrations by the motion of a surface having its diameter of a. larger and different order of magnitude than the q'uar- I ble sound vibrations, objects submerged in the sound carrying medium, said objects having surface irregularltles of a slze, large in comparison with a quarter wave length of the sound vibrations, which consists in emitting continuous trains of said ultra-audible sound vibrations. in the direction ofsaid object thereby producing reflections of discontinuous ultra-audible sound vibrationswhose discontinuity corresponds to audible frequencies and receiving said discontinuous ultra-audible sound vibrations whereby the discontinuity of said discontinuous ultraaudible sound vibrations allows an audible sound.

5. The method of detecting submarines and other submerged objects which comprises the emission of a long train of ultraaudible vibrations against such object whereby the reflected train of ultra-audiblevibrations interfering with the emitted train produce beats of an audible frequency by the interference fringes and causing the response of an indicator to said beats. u

6. The method of determining the distance of submerged objects and surfaces which consists in emitting a high frequency sound Wave, receiving the emitted sound Waves when reflected from the object, causing beats to be formed by heterodyne action,

high frequency generator, a double contact key normall closing said motor circuit and opening sai generator circuit, andclosing said generator circuit when theapparatus is in operation.

9. The method of generating a beam of compressional waves'which consists in emitting high frequency compressional wavesfrom a source, said source having a substantially plane radlatlng surface, large 1n comparison to a quarter wave length of the compressional wave transmitted.

10. The method of varyingthe spread of a beam of compressional waves which consists in emitting high frequency com ressional waves from a source, said source aving a substantially plane radiating surface, large in comparison to a quarter Wave length of the compressional wave, changing the frequency of the source whereby the spread of said beam is changed.

11. The method of generating a beam of compressional waves'which consists in emitting high frequency compressional waves from a source, said source having a substantially planeradiating surface large in comparison tothe wavelength of the compressionai wave transmitted.

12. The method of detecting'ultra-audible sound vibrations which consists in utilizing at a receiving station the received ultra-audible sound vibrations to generate electrical vibrations of ultra-audible frequency, generating, from an independent source, electrical vibrations of a frequency slightly different from the frequency of the vibrations to be detected, producing beats between the electrical vibrations produced by the ultra-audible sound vibrations to be detected and the electrical vibrations produced by the independent source, said beats being of audible requency, an indication by said beats.

REGINALD 'FESSENDEN.

and producing 

